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Scientists discover gene for wheat resistance to Ug99
Ug99 race of pathogen showed that changes in the
The world's food supply should be a little more plenvirulence of existing pathogen races can become a
tiful thanks to a scientific breakthrough, according to
huge problem."
excited university wheat researchers.
As a first line of defense, wheat breeders and reEduard Akhunov, associate professor of plant pasearchers began looking for resistance genes among
thology at Kansas State University, and his colleague,
those that had already been discovered in the exJorge Dubcovsky from the University of Californiaisting germplasm repositories, he said.
Davis, led a research project that identified a gene
that gives wheat plants resistance to one of the
"The Sr35 gene was one of those genes that was dismost deadly races of the wheat stem rust pathogen covered in einkorn wheat grown in Turkey,"
Ug99. This rust was first discovered in Uganda in
Akhunov said. "Until now, however, we did not
1999.
know what kind of gene confers resistance to Ug99
in this wheat accession."
The discovery may help scientists develop new
wheat varieties and strategies that protect the
To identify the resistance gene Sr35, the team
world's food crops against the wheat stem rust path- turned to einkorn wheat that is known to be reogen that is spreading from Africa to the breadbas- sistant to the Ug99 fungal strain. Einkorn wheat has
kets of Asia and can cause significant crop losses.
limited economic value and is cultivated in small areas of the Mediterranean region. It has been replaced
Other Kansas State University researchers include
by higher yielding pasta and bread wheat varieties.
Harold Trick, professor of plant pathology; Andres
Salcedo, doctoral candidate in genetics from Mexico; Researchers spent nearly four years trying to identify
and Cyrille Saintenac, a postdoctoral research associ- the location of the Sr35 gene in the wheat genome,
ate currently working at the Institut National de la
which contains nearly two times more genetic inforRecherche Agronomique in France. The project was mation than the human genome.
funded by the U.S. Department of Agriculture and
Borlaug Global Rust Initiative.
Once the researchers narrowed the list of candidate
genes, they used two complimentary approaches to
The team's study, "Identification of Wheat Gene
find the Sr35 gene. First, they chemically mutagenSr35 that Confers Resistance to Ug99 Stem Rust
ized the resistant accession of wheat to identify
Race Group," appears in the journal Science.
plants that become susceptible to the stem rust
pathogen.
It identifies the stem rust resistance gene named
Sr35, and appears alongside a study from an Austral- "It was a matter of knocking out each candidate
ian group that identifies another effective resistance gene until we found the one that made a plant susgene called Sr33.
ceptible," Akhunov said. "It was a tedious process
and took a lot of time, but it was worth the effort."
"This gene, Sr35, functions as a key component of
plants' immune system," Akhunov said. "It recogniz- Next, researchers isolated the candidate gene and
es the invading pathogen and triggers a response in used biotechnical approaches to develop transgenic
the plant to fight the disease."
plants that carried the Sr35 gene and showed resistance to the Ug99 race of stem rust.
Wheat stem rust is caused by a fungal pathogen.
According to Akhunov, since the 1950s wheat breed- Now that the resistance gene has been found,
ers have been able to develop wheat varieties that
Akhunov and colleagues are looking at what proteins
are largely resistant to this pathogen. However, the are transferred by the fungus into the wheat plants
emergence of strain Ug99 in Uganda in 1999 devas- and recognized by the protein encoded by the Sr35
tated crops and has spread to Kenya, Ethiopia, Sugene. This will help researchers to better understand
dan and Yemen, though has yet to reach the U.S.
the molecular mechanisms behind infection and develop new approaches for controlling this devas"Until that point, wheat breeders had two or three
tating pathogen.
genes that were so efficient against stem rust for
decades that this disease wasn't the biggest concern," Akhunov said. "However, the discovery of the